Fluorescent lamp and coating therefor



Now 18, 1941. P. J. KAYA'IZT FLUORESCENT LAMP ANDCATING THEREFOR I Filed .iul ls, 1939 iflwENToR ffa yai" I ORNEY Patented Nov. 18 1941 Philip J. Kayatt, New York, N. 2., asslgnor to Harry 0. Zann, Atlantic Beach, N..Y.

Application July 13, 1939, Serial No. 284,268

4 Claims.

This invention relates to electrical glow lamps and. more particularly to such lamps of the cathode glow type wherein the visible light is at least partly produced by fluorescence.

In the art of electric illumination use has been made of lamps wherein at least a portion of the lightcame from the fluorescence of certain .materials under the influence of an electric discharge produced in a gas such as mercury vapor or one of the noble or inert gases. However the prior art has found it necessary in such cases to use a discharge of the positivecolumn type, needing for the production of such discharge either a voltage much higher than that available in the customary household distribution circuits, or else the provision of special electrodes which emit electrons to bring about the production of such a positive column discharge, and which require special means in order to heat them sufiiciently to bring about such electron emission.

Fluorescent tubes of the prior art have accordingly sufiered'from the disadvantage of requiring ancillary apparatus such as transformers, re-'- a tors, electrode heaters, and the like, and could not be made with a single standard type base so that they could be directly substituted for a lamp of the usual incandescent type, in a household light socket. On the contrary, such tubes have required the use of one or more special type sockets, in orderto bring to the tube the high potenand a fluorescent light eifect in such fashion that upon the connection of such lamp directly to circuits carrying voltages of the order of 110 volts, the lamp will immediately commence to operate and will continue in operation thereupon, without the existence in the lamp or in any ancillary apparatus connected thereto of voltages substantially higher than the voltage of the lines to which it is connected.

Another purpose of this invention s to utilize the anode surface of a glow lamp of thetype described as an additional source of illumination. When a lamp of the cathode glow type is connected to direct current household mains of usual voltages, only the surface of the cathode will be covered with a glow discharge, and the anode will remain dark, while in the case of the lamp of my invention connected under such circumstances, the anode will likewise glow and emit additional light, without in any way detracting without the consumption of any additional amount of electrical energy. In this fashion my lamp operates as a light producing device of increased efflciency.

A further object of 'my invention is to provide a lamp which shall be capable of being mounted in a two circuit base of the conventional type, so that it can be directly connected to lighting circuits of the order of 110 volts, by the simple insertion of such base in a conventional receptacle, and without theneed of any additional circuit connections, so that the lamp of my invention may readily and easily be substituted for a lamp of the usual incandescent type by a household consumer of electric current, without the need for the services of one skilled in the electrical art in order to connect thereto special circuits or ancillary apparatus.

A further purpose of this invention is to pro vide for domestic and industrial use a low voltage glow lamp simultaneously emitting light of more than one color and thereby afiording novei and attractive multi-c'olor efiecta Another object oi. this invention is to afford. a glow lamp exhibiting a design or pattern which will glow with difierent colors in difierent portions thereof. v

Yet another purpose of my invention is to pr ze vide a glow lamp including asource of fiuora cent light, which lamp shall not require any a iliary starting or operating circuits demanding additional conductors entering the lamp base.

Yet a further purpose of this invention to provide a glow lamp of the type described which hazards of fire and/or shock are substau tially eliminated by so constructing the lamp that no high voltages are needed for itsstarting or operation.

Referring now to the drawing hereunto 'appended, for the better understanding of my in vention:

Fig. 1 is a side elevation partly in section of one form of the lamp of my invention, particularly suited for use upon D. C. supply circuits. Fig. 2 shows also in side elevation and partly in section, the bulb of another form of my invention, suited particularly for use upon A. C. supply circuits. f

' Fig. 3 shows in elevation the bulb of another embodiment of my invention in the form of an ornamental lamp. Fig. 4 shows a lamp having one of the electrodes fluorescing on one side only.

from the illumination of the cathode, and also A glass bulb In, of any suitable shape, is provided with a re-entrant supporting stem ll of conventional type, although it is to be understood that any other method of supporting the internal elements of the lamp may be employed, as known to those familiar in the art. In the form of Fig. 1, two electrodes [2 and I! are mounted upon the stem and are connected by wires I4 and I5 respectively to thetexterior shell l6 and central contact button ll, of a conventional screw base ll. Interposed in series between one of these leads I5 and the base. is a resistor Is, for limiting the current flow to the electrodes to a suitably safe value. This resistor may be of any type familiar to those skilled in the art, and may be made so small in size as to readily be enclosed within the base, without unduly heating the same, owing to the high efliclency of the lamp of my invention.

1 direct cathode glow produced by various gases On the inner surface of electrode I2 I have illustrated a coating 20. For purposes of clarity this coating is here shown disproportionately thick, but it is to be understood that in the actual structure, this coating will ordinarily be only of .a thickness a fractional part of that of the electrode upon which it is spread. This coating is formed of materials which arecapable of fluorescence under the influence of ultra-violet rays or electrical discharges in rarifled gases. Such materials are already known in the art and I shall hereinafter describe in detail a typical material of this type and the method of its application to the electrode. Electrode l3 may be of any suitable type which is suited to initiate and maintain electron emission under tensions of the order of 110 volts. The preparation of an electrode of this character is fully described in my United States Patent 2,084,911, but I do notlimit myself to an electrode prepared according to this particular method, provided only that the electrode fulfllls the requirements of satisfactory electron emission upon a low voltage and when become fluorescent or luminescent. The exact modus operandi by which such coating is excited and mixtures thereof is familiar to those skilled in the art and it is thought unnecessary to describe herein in detail such mixtures. Suitable gas mixtures and pressures are set forth in detail in my patent above referred to, but as above indicated, I have found that fluorescence is promoted by the presence of argon or mercury vapor,

whatever other gases may make up the bulk of the filling. It is possible to make the entire filling of one gas such as argon, although better starting and more efllcient operation especially upon low voltages, is found to occur when mixtures ofmore than one gas are employed.

Referring now to Figure 2, I have here shown a lamp whose two electrodes 2| and- 22 are respectively coated over only a portion of the surface of each with layers 23 and 24 of fluorescent v material, of a thickness exaggerated in the drawing for purposes of clarity. The portions of each electrode not covered by the fluorescent material indicated at 23' and 24 are treated so as to afford electron emission. when a lamp of this form' of my invention is connected to a source of A. C., the electron emitting portions of the electrodes will glow with a cathode discharge of a color determined by the gas mixture present,

' while the coated portions of the electrodes, bearinto luminescence is not precisely known, but' probably it is partly by the impingement thereupon of ultra-violet light, and possibly also partly by the direct action thereupon of the electrical discharge. That ultra-violet light is at least partly concerned in the production of the luminescence seems to be borne out by the fact that such light production is at its maximum when the gas within the bulb is chosen to promote the production of ultra-violet light, and also by the fact that the luminescence is relatively feebler on portions of the coating which may be shielded from the direct rays emitted by the other glowing electrode. However. I do not limit myself to any particular theories involved in the production. of

ing the fluorescent material thereupon, will glow with the color which the particular fluorescent material may give rise to when excited in the particular gas mixture present. Accordingly the entire surface of both electrodes will glow with light which may be of morethan a single color, 1. e., the electrodes will appear differently colored on the coated and the uncoated portions, rwpectively. This type of lamp according to my invention may be used upon D. C. circuits, but

' and partly produced by secondary fluorescence.

In Fig. 3 I have illustrated a form of my invention which is similar in principle to that of Fig. 2, but wherein I have utilized the dual color glow to give certain novel ornamental effects. In this construction supporting wires 25 and 26 are made to simulate the stems of a plant, and each such stem bears thereupon leaves 21, 21 and blossoms 28, 28. The leaves are coated with fluorescent material according to my invention, while the blossoms are treated so as to give electron emission. Accordingly the leaves will glow by fluorescence, which may be made to present a green color, if so desired, while the blossoms will have the cathode glow color characteristic of the gas filling used in the bulb. Such a lamp will operate upon D. C. mains, but certain blossoms which happen to be located upon the anode supporting wire will of course fail to glow, although the leaves upon the anode stem will glow, so that such type lamps have been found to be satisfactory even when used uponD. C. mains. It

is also possible to make the entire simulacrum of a plant, including both the coated and the un,-' coated portions thereof, function asa cathode, and to supply in some other portion of the bulb an anode which shall not form a part of the glowing design, in case that it is desired that the entire plant shall glow when the lamp is operated upon I). C. current supplies.

The form shown in Fig. 4 is similar to Fig. 2, except that electrode 22 has been replaced by an electrode 29 extending horizontally so that both the fluorescent and non-fluorescent sides of electrode 2| will li e visible.

While it isf'possible to construct a. .lamp according to the foregoing description by methods ofv manufacture known in the art, yet I have found particular advantages are to be gained when the following process of manufacture is .followed.

The electrode material may be any metal or alloy which has been found suitable for glow electrode construction, but I prefer to use some form of iron, such as that known under the them while in contact with an atmosphere contaming oxygen to a degree suflicient to cause oxidation of the surfaces thereof, and especially inaccordance with the detailed steps of the process set forth in my issued patent above referred to, so that there is produced upon the surface thereof a coherent coating consisting of a substantially black 'oxid or mixture of oxids of iron, autogenously produced from the actual body the electrodes themselves.

There are two methods which I have found possible to use in the application of the fluores- I cent coating to the electrodes; I shall first describe the method employing an organic binder such as amyl acetate, butyl acetate, and similar substances, ofwhich many varieties are familiar in the art. The fluorescent material may conveniently be chosen from a large group of compounds also familiar in the fluorescent art. Suitable materials include salts such as silicates of calcium, zinc, beryllium and cadmium, tungstates of calcium or samarium, or various complex salts including more than one metal in their composition.

The solid fluorescent material is ground to a degree of fineness suitable for suspension in a vehicle such as the organic acetates above mentioned, and mixed therewith, with or without the addition of a small amount of pyroxylinor nitrocellulose. As an illustrative mixture, I have found a suspension. of to 40 gramsof Willemite in 200 to-400 cc. of butyl acetate, with'the addition of 507to milligrams of nitro-cellu- I lose to be suitable. This mixture is sprayed or brushed upon the dry electrodes at room temperature, or at a temperature very slightly higher, su'clias F. to F. The electrodes are thorou h y dried at this same temperature and then are heatedto about 500 F., although this last mentioned temperature will vary according to the particular fluorescent materials which are I used; During this'heating the pyroxylin'will decompose, becoming brown and thendisappear ingto leave a coating usually whitish under day- I flight: n v

After cooling in dry air, the electrodes are now ready to have applied thereto, or to such portions thereof as may be desired, the electron emitting coating. This portion of the process may be practiced according to the disclosures of myv pat- 5' ent above mentioned, or by any other method familiar to the art.

I have found it possible to dispose with organic binders of the type above mentioned in the ap-' be sprayed upon the electrode which latter has upon its surface a slight degree of moisture, the acetone will rapidly evaporate and will leave the coating in an adherent condition upon the electrode. I prefer to heat the electrode to about 120-130- F. and either to deposit a slight film of moisture thereupon, as by condensation, or by spraying thereupon a slight amount of water at the same time that the acetone suspension of the fluorescent material is being sprayed thereupon.. I have found the adherence of the powdered material to the surface of the electrode to be greatly promoted to a wholly unexpected degree by this presence thereupon of a trace of moisture, although the reason therefor isnotat present fully understood.= After application of material by this last described process, the electrode is ready to have the electron emitting coating applied thereto by any suitable process, such as that above referred'to in connection with the method of coating using organic acetates.

While not confining myself to any particular theory, I have found that coatings produced by the acetone process are superior in performance -to those produced by burning off an organic binder at a necessarily high temperature, possibly due to some undesirable reaction taking place between such binder and the fluorescent material at such elevated temperatures as are needed in order thoroughly to remove a binder of this organic nature.

. v The mounting, exhaust and gas-filling of the lamps of my invention may be practiced as known to those skilled in the art, as described, for example, in my issued patent above referred to. .While I have described my fluorescent material as applied to one or more of the electrodes of my lamps, yet it is possible to apply such material to other portions of the lamps, such as to a dead element therein, or to portions of the glass walls of the tubes, such as the stems, where it will likewise glow upon excitation by the cathode glow primarily produced upon trodes of such lamps.

I claim: 1. An ornamental electric glow lamp including a metallic electrode formed to simulate a natural object. substantially all the active surface of said electrode being covered with a first layer of an autogenous oxid of the metal base thereof, part of said electrode bein'gcoated with emissive material so as to exhibit a cathode glow' thereover and another part of said electrode being coated with a fluorescent material so as to glow with a color differing from said cathode glow, whereby the natural colors of said object are simulated when said lamp is illuminated, and whereby said differently colored portions of the glowingelectrode occupy discrete areas thereof. 3 l5 2. A glow lamp comprising a transparentv ening at least one easily ionizablegas chosen from the groupcomprisedby the noble gases and mercury vapor, electrodes supported from said envelope within said atmosphere and connected to said base, said electrodes having upon substantially all the active surfaces thereof a first coat ing layer produced by autogenously oxidizing a portion of the actualelectrode material insitu, an emissive coating covering a portion of said electrodes and a fluorescent coating covering another portion of said electrodes, whereby cathode glow and fluorescence are simultaneously displayed by difl'erent portions of said lamp when excited by current derived from said socket.

3 In a low voltage electric glow lamp, a metallic electrode being primarily coated with an autogenous oxid of the metal base thereof and being secondarily partly coated with emissive material so as to furnish a cathode glow thereupon when supplied with current in a suitable gaseous atmosphere, and partly coated with a fluorescent material so as to furnish secondary luminescence from said fluorescent material when said fluorescent material is excited by radiation from said cathode glow, said two secondary coatings being upon discrete portions of the electrode.

4. A multi-color glow lamp adapted to operate upon low voltage lighting circuits, comprising a, transparent bulb, a mixture of gases-therein, including at least one of the gases chosen from the group of inert gases, a plurality of metallic electrodes lying within said bulb and surrounded by said gaseous mixture, said electrodes being substantially entirely covered with a first layer of a metallic oxid produced by the autog- V trode, some portion thereof being coated with 

